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Shark Research

04 Nov Shark Research

Shark Research

Movements of Sharks Associated With Cage Dive Ecotourism

Principal Investigators: Carl Meyer & Kim Holland

Project Overview
Concern exists that commercial shark cage diving conducted 3 miles offshore from Haleiwa Harbor increases the risk of shark attack on swimmers, surfers and divers along the North Shore of Oahu (Hawaii). Much of this concern is based on the belief that sharks associated with these commercial tours follow the tour boats back toward shore whenever the boats leave their offshore operation sites. We are using cutting edge technology to track the long-term movements of sharks captured at the cage diving sites and evaluate the public safety implications of these operations.

Research Questions
We are addressing the following specific questions:
(1) How often do sharks visit the cage diving sites and how long do they stay?
(2) Do sharks captured at the cage diving sites ever come into shallow inshore areas utilized by people?
(3) Do sharks follow the cage diving boats back toward harbor?
(4) How far do sharks that visit cage diving sites range?

Methods
We captured 30 sharks (Galapagos and sandbar sharks) at cage diving sites and surgically implanted them with small ultrasonic transmitters. We stationed underwater listening stations (acoustic receivers) at the cage diving sites, at the entrance to Haleiwa harbor channel and at surf breaks along the North Shore of Oahu. We are using this system to remotely track shark movements at multiple locations along the Hawaiian archipelago. The system consists of small, underwater receivers that listen continually for the presence of sharks implanted with coded pulse acoustic transmitters (within a detection range of up to 1000m). The receivers are periodically retrieved by divers and downloaded to find out which sharks have visited, when they came and how long they stayed at each location.

Preliminary Results
Galapagos and sandbar sharks are the most common species seen at cage diving sites (98% of all sharks observed). These species are rarely implicated in attacks on humans. Sharks remain at cage diving sites throughout the day and disperse at night. Sharks that visit cage diving sites also migrate seasonally to deep waters off the West side of Oahu. Inshore movements by sharks associated with cage diving operations are extremely rare. There is no evidence of sharks following boats back to the harbor. Current cage diving operations appear to pose no significant threat to public safety.

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Daily Research and Data collection
Daily observations made during the tours are invaluable. Sharks are not easy to study; following and watching sharks over a stretch of many years for the sake of research would be nearly impossible to finance. Especially considering that shark research is tragically under funded. To truly understand a population of sharks, they have to be observed and studied over longer periods of time.
Obviously it is difficult to follow sharks around. The ocean is difficult for man or equipment to master. Sharks are shy and usually avoid human interaction.

During the shark tours, important data is collected on a daily basis. Count of each species of sharks, distribution and behavior or each species, along with environmental factors such as tides, currents, moon phases, weather and wave patterns, which all can have an effect on the fish population and behavior.
Guests help by reporting observations of anything that passes by in the deep, visible only from inside the cage, and not from the surface.

We also make note of other fish life that occur around the site, such as Mahi Mahi, Tuna, Opelu, Jellyfish and even the occasional passing by of dolphins and whales. It is most interesting to watch the behavior changes in the sharks depending on what other fish or mammals show up.

Unusual sightings such as hammerhead sharks or whale sharks are reported to NOAA. Floating Garbage is picked up.

Cross Pacific Data
When the Great White Shark showed up Dec.. it was a great opportunity for us to connect with researchers across the Pacific and as far as South Africa. Images of the shark were compared to see if the individual was recognized to be from any of the well-known Great White locations of the Farallon Islands, Guadalupe Island or South Africa. Markings on the side of the shark and her enormous size (20 ft) made her easy to identify. There are not many females of this size left in the world. Nevertheless, she was not recognized by anyone.
It raised many questions as to why she was in Hawaii, where she came from and where she was going. Questions we hope to answer through continued support of tagging projects and an increase of listening stations across the waters of the State of Hawaii.

As recent as a few years ago, the common assumption was that there are no Great White Sharks in Hawaii, however the existing listening stations have been able to proof that this is not the case. In the last year alone, 5 different Great Whites passed by the North shore. And that shows only the ones that were tagged.
This shouldn’t instill fear of the North Shore, because it is obvious that the Great Whites passing by, most likely in the deep channels, as they prefer cold water. They don’t seem to be hanging as they would surely be spotted more frequently by fishermen and recreational users of he ocean.

If fear of sharks persists, then the only way to protect sharks and humans is to get more information and data and sharks. You can’t manage or protect something you don’t know.